Comparison of mass transfer parameters inside a USEPA flux hood for two VOCs.

Odorous emissions from area sources at wastewater treatment plants have become an environmental issue due to negative impacts on neighboring communities causing annoyance. Enclosure devices (such as dynamic flux chambers) have been used as direct methods to estimate area source emission rates from liquid-gas surfaces. Previously, model compounds have provided information about the internal mass transfer behavior of these sampling devices and the parameters estimated for certain model compounds that can be adapted for other compounds with similar liquid-gas partitioning properties. Acetic acid and butyric acid (both gas-phase-controlled compounds) were compared in order to assess the validity of adapting results from one compound to another. Mass transfer parameters for acetic acid and butyric acid were determined for a USEPA flux hood using a sweep air flow rate of 5 L/min. Mass transfer rates estimated for butyric acid, using the mass transfer parameters of acetic acid, were of the same order of magnitude as the experimental butyric acid mass transfer rates.